Non deterministic

[Timisorean]

Add support for :non-deterministic (and thus the oneof keyword).

This is done by modifying the structure of the AST:

         ┌─────────────── EffectRoot ─────────┐
         │                                    │
         ▼                                    ▼ 
EffectRootNonDeterministic──────────►EffectRootDeterministic

Here EffectRootDeterministicis equivalent to EffectRootbefore changes.

Additionally, the effect EffectOneof is introduced. It has one attribute, effects, which is a list of all the possible effects of the action.

TODO:

• Check compatibility in mimir